Covalent Synthesis of Two Hybrids Composed of Dawson-Type Polyoxometalate and Porphyrin with Remarkable Third-Order Optical Nonlinearities Reflecting the Effect of Polyoxometalates

Abstract

Two new porphyrin-polyoxometalate hybrids, namely, [(CH)N]H[{COHNC(CHO)PVWO}CNH]·CHCN 1, bearing two covalent-bonded Wells-Dawson-type polyoxometalates (POMs), and [(CH)N)]H[COHNC(CHO)PVWO{CHN}]·CHCN 2, bearing one covalent-bonded POM, have been synthesized and thoroughly characterized by means of elemental analysis, powder XRD, FT-IR, H (P, V) NMR, MALDI-TOF-MS, UV-vis spectra, and cyclic voltammetry measurement. Experimental results demonstrate that while all the compounds show remarkable third-order optical nonlinearities, the hybrids 1 and 2 are superior to their corresponding porphyrin precursors (molecular second hyperpolarizability γ = 8.0 × 10 esu for 54-N-N'(1,3-tetrahydroxy-2-(dihydroxymethyl)propan-4-diyl)benz-diamide,10,15,20-triphenyl porphyrin that is the precursor for the hybrid 1, γ = 2.6 × 10 esu for 54-N-(1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)benz-amide,10,15,20-triphenyl porphyrin that is the precursor for the hybrid 2), and the hybrid 1 (γ = 12.9 × 10 esu) is superior to the hybrid 2 (γ = 12.2 × 10 esu) reflecting more POM moieties covalently bonded to the porphyrin moiety exerting more significant influence on the third-order optical nonlinearities. Meanwhile, attachment of POMs on the porphyrin results in significant fluorescence quenching (fluorescence intensity is decreased 97% for the hybrid 1 and 80% for the hybrid 2 with respect to that of their corresponding porphyrin precursors) indicating strong electron transfer from porphyrin moiety to the polyoxometalate moiety. Lower transition energy, small energy difference between singlet and triplet excited states, and faster intersystem crossing (ISC) process of the hybrids are favorable to enhance the NLO responses of hybrids 1 and 2 resulting from the facile electron transfer from the porphyrin moiety to the Dawson POM moiety when the hybrids are subjected to laser irradiation, which is thought to be responsible to the superior of the hybrid 1 to hybrid 2 and the superior of the hybrids to their corresponding porphyrin precursors as well.

Shining a light on the photo-sensitisation of organic–inorganic hybrid polyoxometalates

“…This journal is © The Royal Society of Chemistry 20xx To date, this vis-exo strategy has been used to creatively explore a range of photo-and electro-chemical applications, including in non-linear optical materials, [49][50][51] the design of unusual fluorescent probes, 52,53 photovoltaics, [54][55][56] photochromic materials, 53,[57][58][59] and, most prominently, artificial photosynthesis and the generation of solar fuels. 60,61 2.1.…”

Porphyrin–Coumarin Dyads: Investigation of Photophysical Properties and DNA Interactions

“…Porphyrins can be considered to be a versatile class of π-conjugated tetrapyrrolic macrocycles with interesting photophysical and biological properties. These macrocycles have specific applications in light harvesting , and photodynamic therapy. , In the last several decades, many different porphyrin derivatives have been prepared via the peripheral functionalization of meso-substituted porphyrins aimed to enhance the biological and photophysical properties of these molecules . Coumarins are an another group of biologically relevant heterocyclic compounds, which also possess interesting biological properties, such as anticancer, anti-HIV, antimicrobial, and anti-inflammatory activities .…”

TiO2 Nanocoral Structures as Versatile Substrates for Surface‐Assisted Laser Desorption/Ionization Mass Spectrometry

“…Among these, MS is an important analytical technique for accurately determining the structures and compositions of POMs. Both ESI and MALDI have been used as ionization techniques for POMs for MS analysis. Figure a–b shows negative ion SALDI mass spectra of dodecatungstosilicic acid (H 4 SiW 12 O 40 , SiW12) and phosphomolybdic acid (H 3 PMo 12 O 40 , PMo12), which are typical POMs, obtained by using TNC substrates.…”